The present invention relates to a magnetic tape cassette which is utilized in a magnetic recording and replaying apparatus, such as a video tape recorder, and other various kinds of information processing apparatuses.
In addition, the present invention specifically relates to a type of magnetic tape cassette wherein a closing lid unit which covers an opening at a front part of the cassette main body so as to be opened and closed freely consists of three lids.
Further, the present invention also relates to a magnetic tape cassette which is preferably utilized in such as a video tape cassette, wherein a lid lock spring that applies force to a lid lock which locks a lid that covers and uncovers an opening at a front end of a cassette case and an attaching structure thereof are improved.
With further increase in magnetic recording density in recent years, magnetic tape cassettes and video tape recorders (hereinafter referred to as VTRs) have become more compact. As the result, VTRs are used outdoors more frequently in such a case as videotaping scenery and figures. Therefore, the magnetic tape cassettes also specially consider outdoor use and a closing lid unit which consists of two or three lids for covering the front and rear sides of the tape has been utilized as a dust-preventive countermeasure.
FIGS. 1 through 3 show a conventional magnetic tape cassette wherein three lids constitute a closing lid unit for covering an opening at a front part of a cassette main body so as to be opened and closed freely.
This magnetic tape cassette 1 comprises a cassette main body 4 which comprises an opening 2 at a front part for insertion of a tape picking element on the side of such an apparatus as a VTR, a magnetic tape 5 which is suspended over the opening by a tape guide provided at the front part of such cassette 4 and a closing lid unit 7 which is attached to a front side of the cassette main body 4 so that the magnetic tape 5 suspended over the opening 2 will be covered for such an occasion as portable use.
The cassette main body 4 consists of an upper cassette half 4a and a lower cassette half 4b. The closing lid unit 7 consists of three lids, an outer lid (front lid) 9, a top lid (upper lid) 10 and an inner lid (rear lid) 11.
The outer lid 9 comprises an outer lid plate 9a which covers a front side of the magnetic tape 5 suspended over the opening 2 and side plate portions 9b which extend from both sides of this outer lid plate 9a. Supporting axle-pins 9c are provided so as to protrude from the inner wall surfaces of the side plate portions 9b, and such supporting axle-pins 9c are fitted in and supported by pin holding holes on both lateral side portions of the upper cassette half 4a at positions close to the front thereof so as to revolve freely. Therefore, the outer lid 9 revolves freely with the supporting axle-pins 9c as revolving centers.
The top lid 10 comprises a top lid plate 10a which covers an area above the magnetic tape 5 which is suspended over the opening 2, outer lid linking portions 10a that link both ends of this top lid plate 10a at the front edge side thereof to a top edge of the outer lid plate 9a so as to revolve freely and top lid slide pins 10d that protrude from arm portions 10c which extend from the rear end edge of the top lid plate 10a and that engage with top lid guide grooves 13 which are formed on both the lateral side portions of the upper cassette half 4a so as to slide freely.
As shown in FIG. 3, when the outer lid 9 is opened, this top lid 10 moves to the rear end side of the cassette main body 4 to be approximately parallel to the upper surface of the cassette main body 4 while the top lid slide pins 10d move along the top lid guide grooves 13 according to a revolutionary transfer movement around the supporting axle-pins 9c of the outer lid linking portions 10b. The outer lid linking portions 10b are pins which fit in engagement holes 9d (not shown) that are provided in both top edge end portions of the outer lid plate 9a.
The inner lid 11, which comprises an inner lid plate 11a that covers a rear side of the magnetic tape 5 which is suspended over the opening 2, top lid linking portions 11b that link a top edge of this inner lid plate 11a to the top lid plate 10a so as to revolve freely and inner lid slide pins 11c that protrude from both ends of a bottom edge of the inner lid plate 11a and that engage with inner lid guide grooves 15 which are formed on inner lateral side portions of the cassette main body 4 so as to slide freely. In this embodiment, as shown in FIG. 2, the top lid linking portions 11b are pins which fit in supporting holes 10f (not shown) that are provided in supporting pieces 10e which protrude from the top lid plate 10a.
To describe the inner lid 11, when the outer lid 9 is opened, while the top lid linking portions 11b follow the movement of the top lid 10, the inner lid slide pins 11c move along the inner lid guide grooves 15 according to a transfer movement of such top lid linking portions 11b. As shown in FIG. 3, the inner lid 11 follows the opening action of the top lid 10 and retreats to the area above the opening 2.
When the magnetic tape cassette 1, such as described above, is mounted on a VTR apparatus, the side plate portions 9b of the outer lid 9 are pushed upward by a lid opening pin (not shown) which is provided on the apparatus side and, corresponding to the opening action of the outer lid 9, the top lid 10 and the inner lid 11 are opened. When the magnetic tape cassette 1 is removed from the VTR apparatus, the lids are closed in a manner reverse to that of mounting.
To assemble such magnetic tape cassette 1 as having a three-plate closing lid unit 7, the outer lid 9, the top lid 10 and the inner lid 11 are assembled temporarily in advance and then, while the top lid slide pins 10d of the top lid 10 are being fitted in the top lid guide grooves 13 which has been provided in the upper cassette half 4a, the three lids 9, 10 and 11 are attached to the upper cassette half 4a to be followed by attaching of the upper cassette half 4a and the lower cassette half 4b.
In the assembling procedures as above, however, the lower cassette half 4b which houses a large number of components and the upper cassette half are attached last, such operations as positioning of the large number of components housed in the lower cassette half 4b must be carried out at the same time as the operation to fit the inner lid slide pins 11c into the inner lid guide grooves 15 of the lower cassette half 4b; the assembling operation is thus an elaborate process and has obstructed increase in the productivity. This is a first problem in the prior art.
In the above-described magnetic tape cassette 10, a motion locus of the top lid 10 is defined by the top lid guide grooves 13 and, between the sliding surfaces 13a and 13b of such top lid guide grooves 13 and the top lid slide pins 10d of the top lid 10, frictional force that work as a sliding resistance is generated.
Some dimensions and configurations of these sliding surfaces 13a and 13b and the top lid slide pins 10d may hinder the top lid slide pins 10d from sliding smoothly when the outer lid 9 is opened and closed, resulting with difficulty in opening of the closing lid unit 7. For example, a force of pressure angle .theta., which is a force working in a specific direction, acts from the outer lid linking part 10b via such top lid slide pin 10d against the sliding surface 13a that the top lid sliding pin 10d is in sliding contact with and, if such pressure angle .theta. is larger than a certain range of values, the smooth sliding of the top lid slide pin 10d is hindered to result with difficulty in opening of the closing lid unit 7. This is a second problem in the prior art.
There have been a variety of magnetic tape cassettes such as a video tape cassette. Among these magnetic tape cassette is a video tape cassette which is, as the disassembled structure thereof is shown in FIG. 4, of a comparatively small size and utilized for such as DVC.
In this video tape cassette 6, a pair of reel hubs 62 and 63 are disposed inside a lower half 61 so as to revolve, and a magnetic tape (not shown in the figure) is wound around these reel hubs 62 and 63. The magnetic tape, which is guided by tape guides 65 and 66 at positions close to the front of the cassette (left side in FIG. 4) and on both right and left sides, passes an opening 67 on the front side of the lower half 61.
On the rims of the reel hubs 62 and 63 (lower flange rims), teeth 70 and 71 are formed along the entire circumference.
In a space which is formed on a rear part of the cassette and between the reel hubs 62 and 63, a sliding element 72 which constitutes a lock device for locking of revolutions of the reel hubs 62 and 63, reel brakes which are engagement claws and a brake spring 74 for applying a force to the reel brakes are disposed to prevent the magnetic tape from slacking when the video tape cassette 6 is not mounted on a video deck (not shown in the figure) or when the cassette is stored or being carried.
An outer lid 76, an upper lid 77 and an inner lid 78 which constitute the lid unit that covers the opening at the front of the cassette case are attached to the upper half 75 so as to be opened and closed freely.
A lock pin 80 protruded from a lateral side plate 79 of the outer lid 76. A lid lock 82 which locks a lock pin 80 of the outer lid 76 is attached to a lateral side plate part 81 of the lower half 61 so as to revolve freely, and a leaf spring 83 is also attached as a lid lock spring which applies a force to the lid lock 82 toward lock side.
A reference numeral 85 defines an upper flange of the reel hub, and a reference numeral 86 indicates a lid spring 86 attached to a revolving shaft of the outer lid 76. In the figure, no symbols are given to the components beside the principle portions, and the descriptions are also omitted.
The above-described leaf spring 83, as FIG. 5 (a view at a position along section A--A in the direction of the arrows in FIG. 4) shows a magnified view thereof, is appropriately bent so as to have a lateral-side-view configuration including a part 83b that is extended so as to depress the lid lock 82 and a curved part that is extended so as to engage with the lower half.
The curved part 83a of the leaf spring 83, which is extended comparatively largely to a side opposite to the part which depresses the lid lock 82, is inserted by elastic deformation between a rib 88 which protrudes from a bottom wall or lateral side wall of the lower half 61 and a part 87 of a lateral side wall that confronts such rib. Availability of this engagement state enables temporary fastening of the leaf spring 83 before being covered with the upper half 75.
In the conventional video tape cassette 6, however, since the leaf spring 83 has such a structure as to be bridged between the rib 88 and the part 87 of the lateral side wall, an attachment base part which is larger than a part which actually functions as a spring has increased the entire size and consequently caused increase in the cost.
Additionally, the rib 88 has to be formed in the lower half for the attachment of the leaf spring 83. Formation of such rib 88 tends to facilitate generation of shrink marks in the vicinity of the rib 88 when the lower half is molded. This comparatively tends to result with degradation in the molding accuracy of the lower half.
On the other hand, it is comparatively difficult to improve the forming accuracy of the leaf spring 83 which is an elastic component.
As discussed above, the unstable forming accuracy of the leaf spring 83, as well as the degradation of the molding performance of the part such leaf spring is attached to, has aroused a problem of unfavorable efficiency of assembling since the leaf spring 83 is comparatively difficult to be locked securely at the time of attachment. Especially when such as an automatic assembling apparatus is utilized, the conventional leaf spring 83 has aroused a problem of difficulty in automatic assembling. This is a third problem in the prior art.